Have you looked into many resources about transgender men (ie, female to male), because that would be very helpful, and I would recommend that if you're serious about this then you should look into your long-term options that go beyond things we can help you with (do things at your own pace, but this can involve seeing a doctor so that you can take testosterone which will masculinise your features, and maybe having surgery to remove your breasts or to construct a penis, and you can also get legal documents changed with your name and gender). It's important not to rush into anything, but if this is really what feels right for you then it's definitely something to consider. I spend a lot of time out in queer communities so I have a lot of experience with transgender people, particularly youth who are at the early stages of transition (including some close friends, one of whom I talked to about writing this post to get some good info), so feel free to message me if you want anymore info or just want to chat xx
Chest (binding)
What people have mentioned above is called binding and can be done with reasonable safety. Never flatten your chest with ace bandages or tape!!!!!!!! You can buy binders that safely flatten your chest (eg, from
underworks), or you can improvise by wearing a sports bra (if you're between sizes, go for the smaller one, but it's not safe to go too small), or maybe two. Only start for small durations so that your body gets used to it, and gradually increase the time, but never bind for more than 8 hours per day, and never ever leave a binder on when you sleep. You can do permanent damage to your ribs and your skin elasticity.
Hair
Other things you can do are to get a male (or at least androgynous) haircut. Tips for more masculine haircuts: if it's too short, it shows off too much of your face shape and doesn't masculinise, so don't go too short; the back needs to be squared rather than rounded; bangs are your friend; don't tuck hair behind your ears; don't have it hang down in front of your ears, cut that part off. I can't remember any other stuff, but there are lots of small things.
Also on the topic of hair; don't shave anything. Let your pits and legs and anywhere else just grow out.
Dick (packing)
While it's not SUPER important, it can definitely make you feel more masculine to have something in your pants. Most people just go with a sock or something (you might wanna pin it to your underwear because you don't want it falling out), but you can buy prosthetics (called 'packers'). The starter packer is generally the
Mr Limpy because it's super cheap and lasts well. Look at underwear ads and catalogues to work out the best placement in your pants.
Mannerisms
Keep your shoulders back and hips square, don't keep your legs too close together, don't sway your hips too much, and don't use too many hand gestures while talking. Keep your head up and look confident. It's small stuff, but helps a lot.
Voice
Speak from your chest, not your throat. There's not too much I can really add, but youtube has plenty of tutorials on methods of lowering your voice through vocal exercises.
Clothes
Top: Layers are your best friend!!!! They cover up your chest and your body shape. Vests are great. Button-up shirts are good. Very baggy shirts are BAD; sure, they hide your shape, but they make you look smaller.
Bottom: Wear your pants on your hips rather than your waist. That can be difficult with larger hips (especially if you buy men's pants), but helps with your body shape. Also gives more room for packing. Don't wear tight pants; get straight jeans.
That's all I can think of for now, but I'll let you know if I think of anything else or if my friend suggests anything (for info: he's living full-time as male and has had surgery to remove his breasts and has been taking testosterone for two years and now has a very masculine body shape and facial hair and a deep voice and it's amazing how much medicine has progressed to help people live authentically!!).
The trans thing is just something to consider; it may fit you or it may not, and even if it does, you don't have to go through any of the legal or medical stuff if you don't want to. I'm just letting you know some options that people have. Good luck with everything, and message me if you wanna talk more xxx